Device for protection against the sun and application of substance to the skin

ABSTRACT

The invention relates to a device for protecting a skin area against light when detecting and/or treating skin disorders, especially cancer and its preliminary stages, including application of compounds and/or compositions to the skin, in connection with which a photoreactive substance appears in the skin area. The device comprises an opaque foil ( 1 ) forming a cavity ( 4 ) relative to the skin and having edges ( 3 ) engaging the skin, the width of the edges ( 3 ) being determined by formula (I), wherein m=the width of the edge, δ=the penetration depth of the light in the skin, In=the natural logarithm, t=the time of the effect of the light, I 0 =the luminous intensity at the skin surface, and D diffused =the diffused energy dose which is allowed to reach the skin area concerned.

This application is the national phase under 35 U.S.C. § 371 of PCTInternational Application No. PCT/SE99/01154 which has an Internationalfiling date of Jun. 24, 1999, which designated the United States ofAmerica.

TECHNICAL AREA

The present invention relates to a device for protecting a skin areaagainst light when detecting and/or treating skin disorders, especiallycancer and its preliminary stages, including application of compoundsand/or compositions to the skin, in connection with which aphotoreactive substance appears in the skin area.

BACKGROUND ART

Skin cancer may be detected optically by applying a gel, ointment or thelike containing deltaaminolevulinic acid (ALA) to the skin area andletting this mixture act on the skin from 1 to 24 h, after which the ALAmixture is removed. In the skin, ALA is transformed into protoporphyrinIX. When the ALA substance has been allowed to act on the skin,protoporphyrin IX has formed in greater quantities in those parts of theskin area where there is a skin disorder than in the rest of the skinarea. Then the skin area is illuminated by light of a certain wavelengthand intensity. Protoporphyrin IX has such properties that those parts ofthe skin area which have a skin disorder and thus contain a particularlyhigh concentration of the substance, will fluoresce with higherintensity than the other parts of the skin area. The fluorescence isregistered by means of a camera and is evaluated. In order to obtaingood and reliable results, the radiation needs a certain wavelength, andthe chamber which catches the fluorescent radiation must also have therequisite filters so that only light of a certain wavelength will beregistered. ALA, which is easily soluble in water, is applied in anoil-in-water or water-in-oil form or as a gel. Usually, a nurse appliesALA to the patients to be examined, but the patients themselves may alsoapply ALA at home and bandage up the site of application, and then aftera few hours they go to the hospital for detecting of cancer. This wholecancer detection method is described in Swedish patent 9603095-2.

By using ALA, it is also possible to directly attack the changed skincells, for example cancer cells, by special light treatment of the skinarea, which gives rise to phototoxic reactions originating fromprotoporphyrin IX.

Whether such treatment takes place or not, the skin is sensitive tolight after the removal of superfluous gel, even some time after thedetection procedure.

The purpose of applying compounds or compositions comprising ALA is thusto prepare the skin area for subsequent detection of skin disorders,especially cancer and its preliminary stages, by means of fluorescentlight and/or to treat the area with light, a phototoxic reaction takingplace which is injurious to the changed cells, for instance cancercells.

TECHNICAL PROBLEM

The very application itself of compounds and/or compositions, such asALA, to the skin in the above-described manner is easy and causes noproblems. However, there is a difficulty since light has to be shut outfrom the skin area to which compounds and/or compositions have beenapplied so that no unwanted photoreactions will take place. Theseunwanted phototoxic reactions result in uncontrolled treatment andbleaching and may take place both before and after the detectionprocedure. It is also important that the compounds and/or compositionsare applied in correct quantities and that the skin area is notdisturbed during or after the treatment with compounds and compositions.

Solution

The present invention has thus solved the above problem in protection ofthe area at issue against light and provided a device for protecting askin area against light in connection with detection or treatment ofskin disorders including application of compounds and/or compositions tothe skin, in connection with which a photoreactive substance appears inthe skin area, the device being characterised in that it comprises anopaque foil forming a cavity relative to the skin and having edgesengaging the skin, the width of the edges being determined by theformula:$m > {\delta \cdot {\ln \left( \frac{t \cdot I_{0}}{D_{diffused}} \right)}}$

wherein

m=the width of the edge,

δ=the penetration depth of the light in the skin,

ln=the natural logarithm,

t=the time of the effect of the light,

I₀=the luminous intensity at the skin surface, and

D_(diffused)=the diffused energy dose which is allowed to reach the skinarea to which ALA is applied.

Such a device limits the dose of photoactivating luminous energy that isdiffused under the edges and into the area of treatment. The frequentlight which has the greatest penetration depth is to be found in the redarea of the visible spectrum and may, for example, have a wavelength of600-650 nm.

It is suitable that the diffused energy dose is below, for example, 0.2J/cm² to prevent an unwanted photoactive effect on the skin. The widthof the edges may then be 10-20 mm.

Preferably, the photoreactive substance can be protoporphyrin IX, theproperties of which are relatively well known.

Conveniently, compounds and/or compositions containingdeltaaminolevulinic acid (ALA) may be applied to the skin.

An example of compositions comprising ALA is a cream or a gel whichcontains an ALA compound. Another example is deltaaminolevulinic aciditself.

According to the invention, it is suitable that the foil is formable andconsists of metal, metal on plastic or opaque plastic. It is alsoadvantageous if the foil is made of a heat-insulating material, forexample metal foil. This gives a higher temperature in the skin areaconcerned, which results in a better blood supply, and thus oxygensupply to the same. Since oxygen is essential for the phototoxic effectused for the detection, such a plaster contributes to the efficiency ofthe treatment. The higher temperature also has a favourable effect onthe formation of protoporphyrin IX.

Such a device can be used as an application and protection device forapplying compositions and/or compounds to the skin, and protecting thearea at issue against sunlight before and after the detection procedure.

When the device is intended to be used for the application of a certainsubstance, i.e. a composition and/or compounds in connection with whicha photoreactive substance appears on the skin before detection and anoptional treatment, the cavity formed relative to the skin preferablycontains the substance to be applied to the skin. The fact that theapplication takes place in this way ensures that no substance will getoutside of the desired area, for instance, under the edges of the deviceor completely outside of the device. Such a misplaced substance would bemore or less unprotected against light and might then cause skininjuries.

DESCRIPTION OF FIGURES

In the following, the invention will be described in more detail withreference to the accompanying FIGURE, which is a sectional view of thedevice according to the invention applied to a skin area.

DETAILED DESCRIPTION

The FIGURE shows the device according to the present invention with acasing 1, which is applied to the skin 2 and which has edges 3 engagingthe skin 2. The edges 3 may be attached by gluing or by applying abandage on the top of the same. The casing 1, which constitutes the mainpart of the device according to the invention, conveniently consists ofmetal foil, a metal on a plastic foil or opaque plastic, for instanceblack plastic. Suitably, the casing 1 is formed in advance so that acavity 4 is created between the skin 2 and the foil 1. The foil 1 alsoneeds to be formable in situ so that the device may be adapted to areaswhich are difficult to reach and cover, for example adjacent to or onthe nose, near the eye etc. Conveniently, the foil 1 can be thermallyinsulating in such manner that the temperature in the skin area underthe device is kept high. A high temperature entails a good circulationof blood in the skin area, which results in a higher oxygenconcentration. The high oxygen concentration speeds up the phototoxicreactions in connection with subsequent illumination of the skin area.The higher temperature also has a favourable influence on the formationof protoporphyrin IX.

The cavity 4 in the device may be filled with foam plastic, cotton woolor the like, which is capable of retaining the ALA solution. It may alsobe filled with only a cream or gel containing ALA. The cavity 4 may becovered with protective plastic, which is removed before adding ALA. Thedevice may be made in advance containing ALA in the cavity 4, butalternatively the ALA solution is introduced into the cavity 4 justbefore the device according to the invention is applied to the skin. TheALA solution, which is available in an oil-in-water emulsion or awater-in-oil emulsion, conveniently has an ALA concentration of 5 to25%.

The size of the edges 3 of the device is extremely important to therequired result. They have to be so big that light is not diffused inthe skin and into the area which is treated with ALA with a view topreventing high and uncontrolled doses of photoactivating light duringthe treatment.

If the total dose of light which is diffused into the area of treatmentis lower than 0.2 J/cm², no serious injury will arise in the areatreated with ALA. Thus, the energy in the light which is diffused underthe edge, should not exceed 0.2 J/cm² during the time of treatment.

The energy which is diffused under the edge is determined by theintensity I of the light which hits the skin outside of the edges 3, thetime of the skin exposure t, the penetration depth δ of the light andthe width m of the opaque edge 3.

The dose which is diffused under the edge is determined by theexpression. Thus, the size D_(diffused) should be less than 0.2 J/cm².$D_{diffused} = {{t \cdot I_{0} \cdot e}\frac{- m}{\delta}}$

Consequently, the width of m can be determined by the above formula,which in its calculated state yields$m > {\delta \cdot {\ln \left( \frac{t \cdot I_{0}}{D_{diffused}} \right)}}$

This gives a width of the edges 3 of 10 to 20 mm in normal states, forexample in sunlight.

After detection and/or treatment comprising application of compoundsand/or compositions containing ALA, a device similar to the onedescribed above can be used, but this time without ALA in the cavity 4and only with a compress or the like. The area is thus protected fromlight some time after the detection since residues of ALA orprotoporphyrin IX may be left in the skin.

The invention is not limited to the shown embodiment and may be variedin different ways within the scope of the claims. For instance, the formof the device may be varied to fit different parts of the body. Eventhough ALA is used in the described example, also other compositionsand/or compounds may be used, in the application of which to the skin aphotoreactive substance appears. Also other photoreactive substancesthan protoporphyrin IX may be used.

What is claimed is:
 1. A device for protecting a skin area against light when detecting and/or treating skin disorders, including application of at least one of compounds and compositions to the skin, in connection with which a photoreactive substance appears in the skin area, wherein the device comprises an opaque foil forming a cavity relative to the skin and having edges engaging the skin, the width of the edges being determined by the formula: m>δ·ln(t·I ₀ /D _(diffused)) wherein m=the width of the edge, δ=the penetration depth of the light in the skin, ln=the natural logarithm, t=the time of the effect of the light, I₀=the luminous intensity at the skin surface, and D_(diffused)=the diffused energy dose which is allowed to reach the skin area concerned.
 2. The device as claimed in claim 1, wherein the photoreactive substance is protoporphyrin IX.
 3. The device as claimed in claim 1, wherein compounds and/or compositions contained deltaaminolevulinic acid (ALA) is applied to the skin.
 4. The device as claimed in claim 1, wherein the foil is formable and consists of metal, metal on plastic or opaque plastic.
 5. The device as claimed in claim 1, wherein the foil is made of a heat-insulating material.
 6. The device as claimed in claim 1, wherein the cavity formed relative to the skin contains compounds and/or compositions to be applied to the skin.
 7. The device as claimed in claim 6, wherein the cavity formed relative to the skin contains an absorbent material that is capable of retaining the compounds and/or the compositions.
 8. The device as claimed in claim 1, wherein the cavity formed relative to the skin contains a protective material protecting the skin after at least one of detection and treatment.
 9. The device as claimed in claim 1, wherein the dose of photoactive luminous energy which is diffused under the edges and into the area of treatment is below 0.2 J/cm².
 10. The device as claimed in claim 1, wherein the width of the edges is 10-20 mm.
 11. The device as claimed in claim 1, wherein the cavity is covered with protective plastic which is removed before use of the device.
 12. The device as claimed in claim 1, wherein the skin disorders the device protects against include cancer and preliminary stages thereof. 